where \({{\bf {F}}_{\rm {c}}} \in {\mathbb {C}^{{N_{\rm {c}}} \times {N_{\rm {c}}}}}\)  and \({{\bf {F}}_{\rm {t}}} \in {\mathbb {C}^{{N_{\rm {t}}} \times {N_{\rm {t}}}}}\)  are DFT matrices. As \({{\bf {H}}_{\rm {a}}}\)  contains only values in a small delay duration [1]}, we focus on the first \({N_{\rm {cc}}}\)  rows of \({{\bf {H}}_{\rm {a}}}\) , denoted by \({{\bf {H}}_{\rm {s}}} \in {\mathbb {C}^{{N_{\rm {cc}}} \times {N_{\rm {t}}}}}\) , for CSI compression and feedback.
